Resistive Random Access Memory (RRAM or ReRAM) is a non-volatile memory in which a dielectric that is normally insulating is configured to conduct after application of a sufficiently high voltage. The formation of a conduction path in the dielectric typically requires a relatively high voltage. Once the path is formed, the path may be RESET (i.e., broken to provide high resistance) or SET (re-formed to provide a low resistance) by an appropriately applied voltage. As used herein, an operation where a ReRAM cell in a high resistive state changes to a low resistive state during a time tSET is a SET operation. Conversely, an operation where a ReRAM cell in a low resistive state changes to a high resistive state during a time tRESET is a RESET operation.
The ReRAM SET/RESET process conventionally has been purely time-based, that is, during the process a voltage is applied on a wordline/bitline of a ReRAM cell for a fixed time period, tWRITE. However, if the SET time is less than the WRITE time (tSET<tWRITE), there is high current consumption and potentially further stress (overset cycling problems). And if the RESET time is less than the WRITE time (tRESET<tWRITE), there is high voltage stress on the ReRAM cell after the cell transition.